A known method for producing a tetrazole compound is blowing hydrogen azide gas into an imidoyl chloride compound at 200° C. or higher (J. Am. Chem. Soc., vol. 80, 1958, p. 4647). Other known methods include a reaction using sodium azide in an aqueous solvent (J. Org. Chem., vol. 23, 1958, p. 1909); reaction using an aprotic polar solvent such as DMF, acetonitrile or the like (Synth. Commun., vol. 1, 1971, p. 1; J. Org. Chem., vol. 19, 1979, p. 3281; J. Fluorine Chem., vol. 99, 1999, p. 83); and like methods.
However, the method in which hydrogen azide gas is blown at 200° C. or higher may allow toxic hydrogen azide to escape the reaction system, and thus poses great safety risks for industrial scale production. In reactions using a solvent such as DMF, acetonitrile or the like, sodium azide may react with the solvent when heating is necessary. Moreover, since such solvents are water-miscible, large amounts of the reaction product dissolves in the aqueous phase in the post-treatment. Furthermore, when DMF or a like high-boiling-point solvent is used, solvent removal is difficult if the reaction product is liquid. Therefore, these prior-art production processes are not industrially advantageous.
An example of a conventional production process for an imidoyl chloride compound is converting an amide compound into an imidoyl chloride compound using phosphorus oxychloride, phosphorus pentachloride, thionyl chloride or a like chlorinating reagent. However, when an amide compound having a highly electron withdrawing group such as a trifluoromethyl group is used in this method, the reaction progresses extremely slowly, thereby hindering the efficient production of the imidoyl chloride compound.
J. Org. Chem., vol. 58, 1993, p. 32 teaches a process for efficiently producing an imidoyl chloride compound containing a strongly electron withdrawing trifluoromethyl group using a large excess of carbon tetrachloride as a chlorinating reagent. However, this process is environmentally problematic since carbon tetrachloride is highly toxic and is a regulated substance due to its ozone depletion potential.
A known production process that does not use carbon tetrachloride is one that uses ethyl trichloroacetate. This process produces, for example, N-(4-methoxyphenyl)-2,2,2-trifluoroacetimidoyl chloride in a yield of 76% (Japanese Unexamined Patent Publication No. 2003-321431). This method, however, produces solid triphenylphosphine oxide in a weight-based amount twice or more than that of the desired product, and the removal thereof is difficult. Moreover, since the yield is only 76%, this is not an industrially advantageous process.